Thinly nickel-plated steel plate



Jan. 3, 1967 HIDEJIRO ASANO ET AL 3,295,936

THINLY NICKEL-PLATED STEEL PLATE Filed Nov. 29 1965 a 1 1 v 0.02 0.04 0.06 0.08 0.10 micron Thickness of plating INVENTORS Hide/fro Asano K yoshi Segawa ATTORNEY:

United States Patent ()filice 3,295,936 Patented Jan. 3, 1967 3,295,936 THINLY NICKEL-PLATED STEEL PLATE Hidejiro Asano and Kiyoshi Segawa, Kiyakyushu, Fu-

kuoka Prefecture, Japan, assignors to Yawata Iron & Steel Co., Ltd., Tokyo, Japan Filed Nov. 29, 1965, Ser. No. 510,229 3 Claims. (Cl. 29183.5)

The present application is a continuation-in-part of application Serial No. 176,113, now abandoned, filed February 27, 1962.

This invention relates to a very thinly nickel-plated steel plate for use in the production of cans having a passive and highly anti-corrosive film. Additionally, it has good solderability, lacquerability and workability.

Tin plates are generally used for producing food cans. Steel plates electroplated with a metal other than tin have not been used as materials for making cans, because there has been found nothing superior to tin in respect to anti-corrosiveness, solderability, lacquerability, poisonlessness and workability. For example, in nickel-plating and the like, in order to obtain sufiicient anti-corrosiveness, it is necessary to make the plating more than several microns thick and it is usual to make it more than 10 microns thick. Such thick nickel plating is not only expensive but also low in workability. From the viewpoint of workability and economy, the thinner the plating, the more preferable it is. However, if the plating is too thin, it will corrode easily.

An object of the present invention is to provide a very thinly plated steel plate which is cheap and has good workability.

Another object of the present invention is to provide a very thinly plated steel plate which is very anti-corrosive,

not adversely effected by heat, easy to solder and lacquer and will not contaminate food.

The above-mentioned objects are obtained, according to the present invention, by a steel plate which is very thinly plated with nickel or a nickel alloy and is surface treated so that a passive film is formed on the whole surface including not only the nickel or nickel alloy surface but also any pinholes which are formed and are highly subject to corrosion.

More specifically, a steel plate is first plated with nickel or a nickel alloy such as Ni-Fe or Ni-Sn' to form a plate of about 0.02 to 0.3 micron thick which is then electrochemically treated on the surface.

The treating solution used in the surface treatment is an aqueous solution of l to 5%, by weight, of sodium salt or potassium salt of dichromic acid or chromic acid or mixtures thereof. It is effective and economical to keep the concentration within a range of 1 to 5%. That is to say, when the concentration is less than 1%, the solution is so dilute that it is diflicult to obtain the desired results and when the concentration is more than 5%, the solution is expensive. The optimum time for cathodetreatment of the material in the treating solution is 1 to seconds at a current density of 1.5 to 4.0 a./dm. for desired results and industrial economy. Above the upper limit of this range, the treatment is uneconomical. Below the lower limit, the effect is poor.

The anti-corrosiveness and lacquerability of the thus obtained thinly nickel-plated or nickel alloy-plated steel plate is as high as or higher than that of a tin plate while the solderability thereof is about equal to tin plate. The plating according to the present invention is so thin that the workability is high and the cost is low. Even when it is exposed to the air at 600 C. for about hours, it is sufiiciently resistant to heat. The surface layer of such plate is thought to consist of dense oxidated film which is very passive.

A comparison of the anti-corrosiveness of the nickelplated steel plate of this invention with a tin plate is shown in the following table. Also shown in the table are a steel plate and a steel plate plated with a 0.06 micron thickness of nickel having no passive film.

RESULTS OF SALT WATER SPRAY TESTS [Tested for 3 hours. Numerals in the table represent rusted areas in Not only Ni but also Cr and Sn are considered to be inert plating metals for food cans and the like. However, the lustrous plating of Sn is difiicult. In order to produce luster, it is necessary to melt the plating after it is made. A thickness of at least about 0.5 micron is required therefor. Thus, a very thin plating is diflicult to produce.

On the other hand, when a steel plate was plated with Cr or a Cr-Fe alloy of a thickness of about 0.04 to 0.3 micron, and then was electrochemically treated on the surface and was subjected to a salt water spray test, an entirely different efiect was produced and the anti-corrosiveness was reduced.

Satisfactory nickel plated steel plate can be produced by the cathode treatment described supra; however, after the cathode treatment the thus-obtained nickel plated steel plate can be subjected to an anode treatment described more fully infra. The result is approximately the same as when only the cathode treatment is used; however, at times slightly more favorable results may be obtained.

This anode treatment is conducted for one second or less at a current density of about 0.1 a./dm. in an aqueous solution of 1 to 5% by weight, of sodium salt or potassium salt of dichromic acid, chromic acid, or mixtures thereof. If a concentration of less than 1% is used the solution is too dilute to give satisfactory results while if a concentration of more than 5% is used satisfactory results are obtained but the solution becomes too expensive for industrial use.

As was pointed out above, the anode treatment should be conducted for one second or less at a current density of about 0.1 a./dm. or less in the chromic acid solution. When the current density or treating time exceeds these values, the results on the plated layer are unfavorable for various reasons.

The following examples are presently preferred specific embodiments and are solely for the purpose of illustration and are not to be construed as limitations of this invention, many variations being possible without departing from the spirit or scope of this invention. All percentages are by weight unless otherwise indicated.

EXAMPLE I.-Ni-PLATING Nickel plating solution:

Nickel sulphate g./l 330 Nickel chloride g./l 45 Boric acid g./l 35 Plating conditions:

Temperature C-.. 50

Current density a./dm. 6

Time seconds 5 Surface treating solutions:

Aqueous solution of 2.0% sodium dichromate. Surface treating conditions:

Cathode treatment at 2.5 a./dm. for 3 seconds.

By the above-mentioned method, nickel platings of various thicknesses were made and the above-mentioned surface treatment was immediately carried out.

The plated steel plate of the present invention made by the above-mentioned method had the following properties.

In the salt water spray test for 3 hours, only 1.0% of the area was rusted and the anti-corrosiveness of the product was higher than tin plate.

The Erichsen value and tensile strength of the product were exactly the same as the original plate. The mechanical properties were not impaired by plating. In this respect, the thus nickel-plated steel plate was superior to the tin plate.

The expansion and adhesiveness of a lacquer on the product were investigated. Though it was difficult to quantitatively indicate, the lacquerability of the product was evidently-higher than of the tin plate.

The results of the soldering tests by the normal method with a solder of SnzPb=30170 are shown in the following table. An aqueous solution of 10% zinc chloride was used for the flux.

Thickness of Ni plating in IL..- 0. 02 0. 04 0. 06 0. 08 0. l Solder rise in mm 20. 18. 0 21. 0 21. 2 20. 5 Adhesiveness in kg./in 9. 0 11. 0 15. 5 18. 0 20. 0

EXAMPLE II.Ni-Sn ALLOY PLATIN G Composition of the plating bath:

Tin chloride 40 g./l. Nickel chloride 300 g./l. Ammonium hydrogen fluoride 55 g./l.

The bath was adjusted to a pH of 2.5 with aqueous ammonia.

Plating conditions:

Bath temperature 60 C.

Current density 3 a./dm.

Anode Alloy of Sn:Ni=6:4. Time 10 seconds. ickness of plating 0.18 micron.

The surface treating solution and treating conditions were the same as in the nickel plating.

The product of the present invention made by the above method had the following properties:

Anti-corrosiveness: In the salt water spray test for 3 hours, only 0.5 to 1.0% of the area was rusted.

Workability: Both Erichsen value and tensile strength of the product were the same as the original plate. Lacquerability: High temperature baking on the product was possible. The la-cquerability of the product was higher than that of a pin plate. Solderability: When an aqueous solution of zinc chloride was used as the flux, the solderability of the product was the same as tin plate.

EXAMPLE III.Ni-Fe ALLOY PLATING Composition of the plating bath:

Nickel sulphate 139 g./l.

COMPOSITION$ OF A'NODES A ND PLATINGS IN PERCENT Auodes Eleetrodeposits of platings Fe Ni Fe l Ni Thus the composition of the electrodeposit of the Fe- Ni alloy plating was difficult to adjust. However, when the electrodeposit was surface-treated according to the present invention, the plates became anti-corrosive, i.e., in the salt water spray test for 3 hours, only 1.0 and 0.5% of the area were rusted in (A) and (B), respectively.

Further, the workability of the product was the same as the original plate and the lacquerability of the product was higher than of the original plate.

EXAMPLE IV.-NICKEL-PLATING Composition of plating bath:

Nickel sulphate 300 g./l. Nickel chloride 45 g./l. Boric acid 30 g./l. pH 4.0. Plating conditions:

Bath temperature 50 C. Current density 4.9 a./dm. Object to be plated Cold-rolled steel sheet.

Under the above conditions steel sheets were plated with nickel, the thickness of the plate ranging from 0.01 micron to 0.10 micron. A portion of these nickel-plated sheets were subjected to a salt water spray test. The thus treated sheets were designated as (A).

Another part of the same nickel-plated sheets was cathodically treated in an aqueous solution of 3% sodium dichromate with a current density of 2.5 a./dm. for 3 seconds. Thereafter, the sheets were subjected to a salt-water spray test. The thus treated sheets were designated as (B). The drawing shows the comparative curves indicating the rusting ratios of (A) and (B).

EXAMPLE v Steel sheets plated with 0.1 micron thick plating of nickel were prepared under the same conditions as in Example IV.

A part of the thus nickel-plated steel sheets was cathodically treated in an aqueous solution of 3% sodium dichromate with a current density of 2.0 a./dm. for 5 seconds.

The 0.1 micron thick nickel-plated steel sheets and the nickel-plated steel sheets cathodically treated were plated in an amount of 3 ing/inch on one side of the surface thereof with a lacquer of the phenol series (lacquer No. S ;1518 M) made by Stoner Mudge Co., U.S.A., and Butyl Cellosolve (thinner) and thereafter heated at a temperature of 200 C. for minutes to form a paint film on one side of the metal. On the paint film 100 checkered squares, having an area of 1 mm. were drawn and Scotch Tape No. 610 was applied thereto. The Scotch Tape was then stripped off. When the Scotch Tape was directly applied to the nickel-plated steel sheet 84 checkered squares of the paint film were stuck to the Scotch Tape and 26 checkered squares of the paint film remained on the surface of the plated metal, while when the Scotch Tape was applied to the surface of the nickel-plated steel sheet which was cathodically treated 84 checkered squares of the paint film remained on the cathodically treated surface.

EXAMPLE VI Steel sheets having a thickness of 0.3 mm. were plated with 1 micron thick plating of nickel under the same conditions as in Example IV.

These nickel-plated steel sheets were subjected to the Ericsson test of 1.8.0. standard. The obtained Ericsson value was 7 mm.

It is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made without departing from the spirit and scope of the invention or sacrificing its material advantages. For example, all references to a thinly nickel-plated steel can include cans having a top made, e.g. from aluminum and other metals and material which are now being used in the production of cans.

Having thus disclosed the invention, what is claimed is:

1. A thinly nickel-plated steel sheet comprising a steel sheet plated with a 0.02 to 0.3 micron thick plating of a material selected from the group consisting of nickel,

nickel-tin alloy and a nickel-iron alloy, said plating :be-

ing covered with a passive film produced by cathode electrolysis of the surface of said plating in an aqueous solution of a chromic acid selected from the group consisting of dichromic acid, the sodium salt of dichromic acid, the potassium salt of dichromic acid, chromic acid, the sodium salt of chromic acid, the potassium salt of chromic acid, and mixtures thereof, at a current density of 1.5 to 4.0 a./dm. for from 1 to 10 seconds. I

2. A nickel-plated steel sheet according to claim 1 wherein the concentration of said chromic acid is from 1 to 5%.

3. A thinly nickel-plated steel sheet comprising a steel sheet plated with a 0.02 to 0.3 micron thick plating of a material selected from the group consisting of nickel, nickel-tin alloy and a nickel-iron alloy, said plating being covered with a passive film produced by cathode electrolysis of the surface of said plating in an aqueous solution of a chromic acid selected from the group consisting of dichromic acid, the sodium salt of dichromic acid, the potassium salt of dichromic acid, chromic acid, the sodium salt of chromic acid, the potassium salt of chromic acid, and mixtures thereof, at a current density of 1.5 to 4.0 a./dm. for from 1 to 10 seconds, followed by anodic electrolysis in said aqueous solution at a current density of not more than 0.1 a./dm. for not more than one second. 7

References Cited by the Examiner UNITED STATES PATENTS 1,513,120 10/1924 Madden 204-56 X 1,998,496 4/ 1935 Fiedler 204-56 3,090,733 5/1963 Brown 29-1966 HYLAND BIZOT, Primary Examiner. 

1. A THINLY NICKEL-PLATED STEEL SHEET COMPRISING A STEEL SHEET PLATED WITH A 0.02 TO 0.3 MICRON THICK PLATING OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF NICKEL, NICKEL-TIN ALLOY AND A NICKEL-IRON ALLOY, SAID PLATING BEING COVERED WITH A PASSIVE FILM PRODUCED BY CATHODE ELECTROLYSIS OF THE SURFACE OF SAID PLATING IN AN AQUEOUS SOLUTION OF A CHROMIC ACID SELECTED FROM THE GROUP CONSISTING OF DICHROMIC ACID, THE SODIUM SALT OF DICHROMIC ACID, THE POTASSIUM SALT OF DICHROMIC ACID, CHROMIC ACID, THE SODIUM SALT OF CHROMIC ACID, THE POTASSIUM SALT OF CHROMIC ACID, AND MIXTURES THEREOF, AT A CURRENT DENSITY OF 1.5 TO 4.0 A./DM.2 FOR FROM 1 TO 10 SECONDS. 